This invention relates generally to energy storage devices, and more particularly, to an apparatus and method for protecting energy storage cells upon occurrence of a short-circuit condition.
The demand for new and improved electronic and electro-mechanical systems has placed increased pressure on the manufacturers of energy storage devices to develop battery technologies that provide for high energy generation in a low-volume package. Conventional battery systems, such as those that utilize lead acid for example, are often unsuitable for use in high-power, low-weight applications. Other known battery technologies may be considered too unstable or hazardous for use in consumer product applications.
A number of advanced battery technologies have recently been developed, such as metal hydride (e.g., Nixe2x80x94MH), lithium-ion, and lithium polymer cell technology, which would appear to provide the requisite level of energy production and safety margins for many commercial and consumer applications. Such advanced energy storage systems, however, typically produce a significant amount of heat which, if not properly dissipated, can result in a thermal runaway condition and eventual destruction of the cells, as well as the system being powered by the cells.
The thermal characteristics of an advanced battery cell must therefore be understood and appropriately considered when designing a battery system suitable for use in commercial and consumer devices and systems. A conventional approach of providing a heat transfer mechanism external to such a cell, for example, may be inadequate to effectively dissipate heat from internal portions of the cell. Such conventional approaches may also be too expensive or bulky in certain applications. The severity of consequences resulting from short-circuit and thermal run-away conditions increases significantly when advanced high-energy electrochemical cells are implicated.
There is a need in the advanced battery manufacturing industry for an energy storage system that exhibits high-energy output, and one that provides for safe and reliable use in a wide range of applications. There exists a further need for a non-intrusive, inexpensive thermal management approach that protects energy storage cells from thermal run-away resulting from a short-circuit condition. The present invention fulfills these and other needs.
The present invention is directed to an in-situ thermal management system for an energy storage device. The energy storage device includes a plurality of energy storage cells each being coupled in parallel to common positive and negative connections. Each of the energy storage cells, in accordance with the cell""s technology, dimensions, and thermal/electrical properties, is configured to have a ratio of energy content-to-contact surface area such that thermal energy produced by a short-circuit in a particular cell is conducted to adjacent and neighboring cells so as to prevent the temperature of the particular cell from exceeding a breakdown temperature. In one embodiment, a fuse is coupled in series with each of a number of energy storage cells. The fuses are activated by a current spike capacitively produced by a cell upon occurrence of a short-circuit in the cell, thereby electrically isolating the short-circuited cell from the common positive and negative connections.